(1) Field of the Invention
The present invention relates to a control circuit for a microwave oven in general and specifically to an independently driven turntable control circuit of microwave oven and a method of controlling the microwave oven.
(2) Description of the Prior Art
A microwave oven is an electric cooking appliance which cooks food by frictional heat through high frequency energy. The water molecules contained in the food, move at high speeds, which produces heat to cook the food. An electronic shower technique using a stirrer fan and a turntable mechanism have been proposed in order to effectively apply the high frequency energy to the food being cooked.
A conventional microwave oven, employing a turntable mechanism, used because of its convenience.
FIG. 1 illustrates a circuit diagram of a microwave oven using the turntable mechanism in accordance with the conventional art. The operation of the microwave oven is now described referring to FIG. 1.
When the door of the microwave oven is closed, a door switch 14 is activated in the ON position, and a first switch 15, interlocked to the door switch 14, is also activated. If a cooking program is input to the microwave oven and the start key is pressed by the user, a control portion 30 turns on a main relay 12, thus entering the cooking operation.
As the main relay 12 is turned ON to apply power to the microwave oven, the control portion 30 controls a power relay 16 according to a cooking program set by the user, and the microwave oven performs a rapid cooking sequence. A lamp 13 is switched on to monitor the cooking state, and a fan motor 17 goes into action for cooling the magnetron 21 and ventilating the cooking chamber. A turntable is driven to apply a uniform distribution of high frequency energy to the food. The turntable motor 18 is operated to drive the turntable. The food placed in the cooking chamber is cooked by high frequencies generated from a magnetron 21 provided to the other side of a high voltage transformer of a magnetron driving portion 20.
Reference numeral 3 denotes a filter that removes a noise contained in the applied alternating current(AC) power source.
The power relay 16 is turned OFF when the programed cooking time is complete. When the door is opened, the door switch 14 is turned off and the first switch 15, connected to the door switch 14, turned off, too. Thus, when the door is opened, the power for driving the magnetron 21, the fan motor 17, and the turntable motor 18, is cut off.
In the conventional microwave oven, as the power driving the turntable motor is cut off after completion of cooking, the user rotates the container of food or the turntable manually to inspect the cooking state or takes the container out of the cooking chamber.
However, when the user tries to turn the container or the turntable manually, it is hazardous to touch the container and the turntable, as it is heated during the heating operation. By manually manipulating the contents in the cooking chamber, spills are practically inevitable. Furthermore, when cooking several items simultaneously, it is inconvenient to take anteriorly placed items out of the cooking chamber.
Based on the above and foregoing, it can be appreciated that there exists a need to obviate the above-described disadvantages of microwave ovens presently available. The present invention fulfills this need.